Wednesday, March 11, 2015

2 Speed Wiper Switch Bypass 77-79 Ford LTD II, Ranchero, Thunderbird, Cougar XR7

It happened to me this morning, the middle of a rainstorm... The dreaded 2 speed wiper switch failure. Nellie (My 1978 LTD II) is my daily driver at the moment, so I had to come up with a fix to get me by while I track down a replacement. While tracking down the switch pinouts I found several references to people trying to use toggle switches without any luck, so I decided to share my solution. This works, and in my opinion is much safer than trying to hot wire the motor from under the hood, which it seems people have tried.

That being said, I must state this disclaimer...

***I am not an electronics expert. I assume no responsibility or liability for any damage to your vehicle or other property for attempting this repair. This is a temporary fix, not a permanent repair. As always disconnect your battery before working on the electrical system***

First thing I want to show you is the pinout continuity test for the switch. I have an entire Adobe file with wiring diagrams and testing procedures for 77-82 Ford wiper systems if somebody wants to suggest a way to share I would gladly do so.



Looking at this the first thing I noticed that any time the wipers were on in low or high the terminals A-G-H had continuity, or were connected together. The only difference between speeds was which terminal C or E was connected to D. I looked at the base of my separated switch.



I noticed terminals A & H were always connected together with a 8 1/4 amp circuit breaker between the two terminals. when the switch was rotated to the low position terminals C&D connected and G&H connected. Turn the switch to high and D&E connected and G&H stayed connected. I was ready to mark my switch socket and wire a bypass.



I discovered Molex .093 male pin crimp terminals fit the female terminals in the Ford factory connecter. These are pretty common. I got mine from a 9 pin molex connecter kit from Radio Shack part #2740229. Napa and Car Quest should have them in their Weather Pack connector supplies. You might be able to raid some from connecters at the junk yards, if you go this route make sure the wire is at least 16ga. Here's a picture of the pin terminal.



I crimped the connecters on lengths of 16ga wire then soldered them. I pushed one into Ford connecter on the vehicle. I then slid a length of heat shrink tube over the wire and pin terminal until no metal was exposed. I repeated that for the remaining leads. Sorry I don't have pictures of that I ran out of light and the half of me hanging out from under the dash was soaked. Here's a very basic circuit diagram I made in MS Paint. I hope it makes sense.



The way I am running it terminal A connects to an ATC (blade style) fuse holder I have a 10 amp fuse in it now, but I am replacing it with an 8amp circuit breaker that fits the holder as soon as I receive it from O'reilly  Auto. The wire exiting from the fuse holder connects to two wires, one plugs into terminal H, the other connects to one side of a toggle switch. The wire from terminal G connects to the other side of the toggle switch. That completes the power side of the wiring. The speed control side is as simple as you want it to be. Make a jumper and connect terminal C&D for low, or terminal D&E for high speed. I included a example of how to wire a SPDT switch to change speeds on the fly, if you have room to run a second switch. The only switch you have to turn off is the power circuit, you will not have park function, but at least you can use your wipers in an emergency while you're waiting on that replacement switch. You could also take 12volts from the terminal G side of your power toggle switch run it to a momentary on push button switch and then to that terminal marked with a "W" and your washer pump will spray.

Please be careful, don't eliminate the circuit protection. Use a circuit breaker of some sorts, no bigger than a 10amp. Be safe!



10 comments:

  1. I tried your solution but it did not work. The wipers move up 2" then cycle down and then up 2" etc. looked at what you have said about G&H continuity in the low speed, however in the diagram you have H connected to one side of the switch and G connected to the other side, this seems contradictory to stating that G&H are to have continuity, should G&H actually be joined with A (ground)? and then to one side of the switch? D is the hot (ignition) wire, should this be joined with C then to the other side of the switch? Your comment appreciated,
    Steve

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    1. Hi Steve,

      Sorry you're having trouble. I'm not sure why this didn't work for you, assuming that there were no other issues with the wiper motor or circuitry, and it was the same non delay 2 speed setup it should work. I'm still running that way myself.

      Let me try to clear up your questions. Inside the switch terminal A and terminal H are always connected using a thermal circuit breaker. When you turn the switch (factory switch) on in either speed contact is made between terminal H and terminal G. I chose to put the switch there to interrupt the H and G terminal so I could turn the wipers on and off. I have terminal C and D connected with a jumper. They do not connect or jump to anything else, this is low speed. If I move the jumper to connect terminal D and E, I have high speed.

      I can go check the terminals after work tomorrow, so we can compare what terminals are hot or grounds if you want. I can take more pictures of the bypass wiring, anything I can do to help.
      Lee

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  2. Hi Lee, I can confirm that the motor is non-intermittent and was working fine until the switch fell apart

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  3. I have the full manual on CD so I can see the wiring diagrams and the same connector pin-outs you have loaded on the blog and they agree with what I have. The only difference is I removed the wiring connector and just have the bare wires, perhaps the connector is necessary for some reason. These two I have wire together D Hot (ignition) is Black/Green, C is Blue/Orange. Then I have A-H wired together and connected to one side of the switch, A is black (ground) H is Green. G Yellow/Red is connected to other switch terminal. So when A-G-H are in continuity they go to ground. Perhaps you could confirm your wire colors?

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    1. I am stumped. We are in agreement on the wire colors. The connector would make no difference because nothing is bridged or connected inside of it. I assume that you have tried a quick test wiring without the circuit breaker between A&H. If not I would suggest that next. However my experience with a weak breaker has the wipers stuttering across the windshield in a full cycle, not reversing. Are your wipers still in the park position? My switch failed while the wipers were on and not parked. I'm not sure this would make a difference, but I don't know for sure. Let me know, I still want to do whatever I can to help you figure this out. Where did you get your CD with the wiring diagrams? I need to invest in a copy myself.

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  4. Hi Lee,
    Thanks for the confirmation. I am going to check my connections again and make sure I have A-G done right.I have wired A-G together and connect direct to one side of the toggle, so the circuit breaker is bypassed. Basically what happens is when the switch is turned on Low D-C have continuity as you clarified in your blog, and A-G-H have continuity, the toggle switch completes the A-G and H circuit to ground, so may I am just not getting the ground properly. The wipers do not park, understandably because that is controlled by the other wires that are no longer plugged in, I just turn the switch off when they cycle down, they did park however before the switch fell apart. Thanks for your help your observation about the continuity that takes place opened my eyes to how the circuit worked. The CD I purchased on line, E-bay I think about a year ago, I have no problem making a copy and mailing it to you if want.
    Thanks again, I

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  5. OK - Low Speed now works...I had to reverse C with G. The wiring schematic shows power going into the wiper motor on the Yellow/Red wire (G) and returning from the wiper motor on the Blue/Orange wire (C). So I connected ignition (D) with G. Then connected A-H to one side of toggle switch and the C

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  6. Replies
    1. I'm glad you got it working! It doesn't make sense to me based only on the internals of my switch, but I never had a matching schematic. I definitely want to look into this more so I can update the blog adding what worked for you. Was your switch still an oem, and do you have its part number? Would definitely appreciate getting a copy of that schematic if you can. Oh and tell me about your car. I can't believe I didn't even ask before now. If you want you can contact me by e-mail at leesltd2@gmail.com.

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  7. How do you get your wipers to reverse

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